Improved means to manipulate fatty acid compositions, from biosynthetic or natural plant sources, are needed. For example, novel oil products, improved sources of synthetic triacylglycerols (triglycerides), alternative sources of commercial oils, especially tropical oils (i.e., palm kernel and coconut oils), and plant oils found in trace amounts from natural sources are desired for a variety of industrial and food uses.
To this end, the Fatty Acid Synthetase (FAS) system in higher plants has been studied. The mechanism of production of "long-chain fatty acids", i.e., fatty acids having a carbon chain length of equal to or greater than 16 carbon atoms (C16), via the acyl carrier protein (ACP)-dependent, plastid-localized FAS of plants is relatively well characterized. However, the mechanism(s) by which plants produce fatty acids having shorter carbon chains, i.e., less than C16 atoms, has remained elusive until the invention described herein.
Medium-chain fatty acids (C8 to C14) are found in some natural plant species in abundance. For example, several species in the genus Cuphea accumulate triglycerides containing medium-chain fatty acids, e.g., Cuphea procumbens, Cuphea lutea and Cuphea inflata. Another known natural plant source of medium-chain fatty acids is the Lauraceae family: e.g., the California Bay (Umbellularia caIifornica), Pisa (Actinodophne hookeri) and Sweet Bay (Laurus nobilis) trees. Other plant sources include Ulmaceae (elm), Myristicaceae, Simarubaceae, Vochysiaceae, and Salvadoraceae.
Medium-chain fatty acids have special importance in the detergent and lubricant industries or in the formulation of edible oils with reduced caloric value or other health benefits. See for example, U.S. Pat. No. 4,863,753 and Barch, A. C. & Babayan, V. K., Am. J. Clin. Nat. (1982) 36:950-962.
As such, a ready source of medium-chain fatty acids, including storage lipids which have incorporated one or more medium-chain fatty acids therein, are desired for a variety of industrial and food use fields. Once the biosynthetic pathway of medium-chain fatty acids in plants is determined, the system can be studied for application in vivo and in vitro. Studies of the mechanism may provide means to further enhance, control, modify or otherwise alter medium-chain fatty acid products or resulting triglycerides and oils. Thus, the elucidation of the factor(s) critical to the natural production of medium-chain fatty acids in plants is desired, including the purification of such factors and the characterization of element(s) and/or co-factors which enhance the efficiency of the system. Of special interest are the nucleic acid sequences corresponding to factors related to the production of such medium-chain fatty acids for applications in genetic engineering.